cp's OEIS Frontend

A189585 Number of permutations of 1..n with displacements restricted to {-4,-3,-1,0,2}.

%I A189585 #8 May 02 2018 15:22:26
%S A189585 1,1,2,4,10,20,37,72,140,277,553,1085,2129,4185,8228,16208,31902,
%T A189585 62747,123449,242860,477830,940205,1849830,3639492,7160647,14088415,
%U A189585 27719015,54537120,107301253,211114467,415365925,817229415,1607893843,3163519669
%N A189585 Number of permutations of 1..n with displacements restricted to {-4,-3,-1,0,2}.
%H A189585 R. H. Hardin, <a href="/A189585/b189585.txt">Table of n, a(n) for n = 1..200</a>
%F A189585 Empirical: a(n) = a(n-1) +2*a(n-3) +a(n-4) +4*a(n-5) +2*a(n-6) +a(n-8) -4*a(n-9) -2*a(n-10) -a(n-11) -a(n-12) +a(n-15).
%F A189585 Empirical g.f.: x*(1 + x^2 + 3*x^4 + x^5 + x^6 + x^7 - 3*x^8 - 2*x^9 - x^10 - x^11 + x^14) / (1 - x - 2*x^3 - x^4 - 4*x^5 - 2*x^6 - x^8 + 4*x^9 + 2*x^10 + x^11 + x^12 - x^15). - _Colin Barker_, May 02 2018
%e A189585 Some solutions for n=11:
%e A189585 ..4....1....1....1....2....1....4....5....1....2....1....1....4....4....1....1
%e A189585 ..3....2....2....5....3....6....2....6....5....3....2....2....2....6....5....2
%e A189585 ..1....3....3....4....1....3....1....1....3....1....7....7....1....1....4....4
%e A189585 ..2....5....4....2....4....2....5....2....2....5....5....5....8....2....2....8
%e A189585 ..5....6....8....3....5....9....3....3....6....6....3....3....3....3....3....3
%e A189585 ..6....4....6....6....6....4...10....4....4....4....4....4....6...10....7....7
%e A189585 .10....8....5....7....8....5...11....7...10....8...11...10....5....5...11....5
%e A189585 ..9....9....9....9...11....8....6...11....8...11....6....6...11....9....6....6
%e A189585 ..7....7....7...10....7....7....7...10....7....7...10....9....7....7...10...10
%e A189585 ..8...10...10....8...10...10....8....8...11...10....8....8...10....8....8...11
%e A189585 .11...11...11...11....9...11....9....9....9....9....9...11....9...11....9....9
%K A189585 nonn
%O A189585 1,3
%A A189585 _R. H. Hardin_, Apr 24 2011